A Radio Resource Control (RRC) layer of a Long Term Evolution (LTE) system is mainly responsible for broadcast, paging, radio resource control, connection and management, radio carrier control, mobility management and terminal measurement report and control. When a RRC is carrying out the radio resource control, connection and management, a downlink RRC message sent by an eNB to a User Equipment (UE) is sent to the UE on a scheduled Physical Downlink Shared Channel (PDSCH) resource, after downlink PDSCH resource is dynamically scheduled through a PDSCH. In order to reduce the overhead of the PDSCH resource of the downlink RRC message, in the LTE system, the downlink RRC message is sent by means of delta signaling configuration, that is, after receiving the RRC message, on the basis of original configuration information, the UE adds, deletes or modifies part of the configuration according to the delta signaling to acquire a complete new configuration, and most of the unmodified configuration information can be sent without using an air interface, thus saving the air interface resource.
FIG. 1 is a flowchart showing a handover in an LTE system. As shown in FIG. 1, in the LTE system, after making a handover decision to carry out the handover, a source base station sends a handover request command to a target base station, through an X2 interface between the base stations or an S1 interface between the base stations and an Mobility Management Entity (MME), wherein context information of the UE in the source base station is carried in the command; after receiving the handover request command, the target base station sends the configuration information for the UE to the source base station through a handover request response command; after receiving the handover request response command, the source base station sends the configuration information for the UE from the target base station to the UE through a handover command; and after receiving the handover command, the UE accesses the target base station according to the configuration information in the command and sends a handover completion command to the target base station after accessing the target base station successfully. FIG. 2 is a flowchart showing a RRC reconstruction in an LTE system, as shown in FIG. 2, when determining to carry out the RRC reconstruction, the UE sends a RRC reconstruction request to a serving base station; after receiving the RRC reconstruction request, the serving base station sends a RRC reconstruction command to the UE; and the UE carries out the RRC reconstruction and returns a RRC reconstruction completion message to the base station after the RRC reconstruction is completed successfully; and the base station will generally carry out a RRC reassignment process again after the RRC reconstruction is completed.
In a connected state, a specific process of the measurement is that: a network side sends a measurement control message to a UE, wherein the measurement control message contains a measurement identity, a measurement object, a report configuration and other measurement-related attribute, and the measurement identity associates the measurement object with the report configuration to form a complete measurement task. The measurement object contains the attributes (for example carrier frequency, a list of neighboring cells and the like) of the measurement object, only one measurement object may be configured by each carrier frequency; and the report configuration contains the attributes (for example event triggering or periodic report, definition on a triggered event (A1, A2 . . . ), times reporting and the like) of the report configuration. The UE carries out a measurement and an evaluation according to the measurement object and the report configuration contained in the measurement control message, generates a measurement report according to a result of the measurement, and reports the measurement report to the network side.
In order to reduce the overhead of the handover and the RRC signaling reassignment after the RRC is reconstructed, the UE carries out the following processing (hereinafter referred to as a measurement task processing) regarding to the measurement task during the process of a pilot frequency handover or reconstruction: when a Measurement Object (MO) configured by a serving cell (a cell before the handover or reconstruction, referred to as a source side) for a UE contains the carrier frequency of a target cell (a cell after the handover or reconstruction, referred to as a target side), the UE processes the measurement object of the carrier frequency on which there is the serving cell and the measurement object of the carrier frequency on which there is the target cell, that is, a measurement identity corresponding to the measurement object of the carrier frequency on which there is the source serving cell, is corresponded to the measurement object of the carrier frequency on which there is the target cell after the measurement task processing is performed and a measurement identity corresponding to the measurement object of the frequency carrier on which there is the target cell is corresponded to the measurement object of the carrier frequency on which there is the source serving cell after the measurement task processing is performed, as shown in FIG. 3, otherwise, the measurement task corresponding to the measurement object of the carrier frequency on which there is the source serving cell is deleted. FIG. 3 is a flowchart showing a measurement task processing in an LTE system, and as shown in FIG. 3, the process of the measurement task processing is specifically as follows: the carrier frequency on which there is a source cell (i.e. the serving cell shown in FIG. 3) has two measurement tasks which are MID#0 (MO#0+RC#0) and MID#1 (MO#0+RC#1) respectively, and the carrier frequency on which there is a target cell (i.e. the target cell shown in FIG. 3) has one measurement task that is MID#2 (MO#1+RC#2). The process is as follows: the two measurement tasks MID#0 and MID#1 of the MO#0 are correspond to the MO#1, i.e. a new MID#0 (MO#1+RC#0) and a new MID#1 (MO#1+RC#1); and the measurement task MID#1 of the MO#1 is correspond to the MO#0, i.e., a new MID#2 (MO#0+RC#2).
The process of the measurement task processing is briefly described by taking the handover as an example. The measurement task configuration information of the UE in the source base station is carried in the handover request command sent from the source base station to the target base station, after receiving the handover request command, the target base station carries out the above-mentioned measurement task processing if the handover request is the pilot frequency handover, and then configures a new measurement task (which is completed through a delta signaling) for the UE based on the processed measurement task, wherein the new measurement task is contained in a handover request response command to be forwarded to the UE through the source base station; after receiving the handover command, the UE carries out the measurement task processing first and then carries out the new measurement task contained in the delta signaling configured by the target base station. In this way, the final measurement tasks of the UE and the target base station are consistent, moreover, as the new measurement task configured by the target base station for the UE is just a delta signaling, the air interface resource can be saved.
In order to provide a higher data rate to a mobile user, a Long Term Evolution Advance (LTE-A) system has proposed a Carrier Aggregation (CA) technology, the purpose of which is to provide a wider wideband for the UE with a corresponding capability to increase the peak rate of the UE. In the LTE system, a maximum downlink transmission bandwidth supported by the system is 20 MHz, while the CA technology aggregates two or more Component Carriers (CC) so as to support a transmission bandwidth of larger than 20 MHz but no more than 100 MHz. The UE of the LTE-A system with the CA capability can send and receive data at a plurality of CCs synchronously, and if it is not noted specially, the UE described hereinafter refers to the UE of the LTE-A system. In the LTE-A system, a UE in a connected state can communicate with a source base station by means of a plurality of CCs (e.g., CC1, CC2) synchronously and specifically identify a carrier by means of a component carrier identity such as a CC ID. The base station designates a Primary Component Carrier (PCC) for the UE through an explicit configuration or according to a protocol agreement, and other component carriers are referred to as a Secondary Component Carriers (SCC); and the serving cell on the PCC is referred to as a Primary Cell (Pcell) and the serving cell on the SCC is referred to as a Secondary Cell (Scell). Non Access Stratum (NAS) information (e.g., such information as Cell Global Identification (ECGI), Tracking Area Identity (TAI) and the like) is acquired by the Pcell; and if a Radio Link Failure (RLF) occurs in a downlink Pcell, the UE needs to carry out the RRC reconstruction. After the UE in the idle state accesses a network and enters into the connected state, the accessed cell is the Pcell. When the UE is in the connected state, a network side can complete the transition of a Pcell through the RRC reassignment or an intra-cell handover, or the network side designates the Pcell during the process of informing the UE to carry out a handover. Thus, a carrier aggregation serving cell and a carrier aggregation neighboring cell may both contain a plurality of carriers, and there is uncertainty in the principle of the measurement task processing in the LTE system, however, no solution has been recorded in the current standards or proposals as to solve this problem. This uncertainty may cause that a difference exists between the measurement task configuration performed by the target base station and the measurement task configuration understood by the UE, thereby causing chaos during the measurement process, so that the base station side fails to acquire a complete measurement result, causing system resource waste as the UE side performs an error measurement process.
Defined measurement events in the LTE system are: an event A1 (the signal quality of the serving cell is higher than a designated threshold), an event A2 (the signal quality of the serving cell is lower than a designated threshold), an event A3 (the signal quality of the neighboring cell is a designated offset higher than that of the serving cell), an event A4 (the signal quality of the neighboring cell is higher than a designated threshold), and an event A5 (the signal quality of the serving cell is lower than a designated threshold 1, and the signal quality of the neighboring cell is higher than a designated threshold 2); wherein the event A4 is unrelated to the serving cell, therefore, the definition on the event A4 is unchanged in the LTE-A system. The events A1 and A2 are measurement events aiming at one serving cell; therefore, in the LTE-A system, each serving cell (Pcell or Scell) has a measurement task of the event 1 and the event 2; the events A3 and A5 may have the two following types: a co-frequency event A3 (or referred to as an A3-SCC) or an event A3/A5. The co-frequency event A3 is defined as follows: the frequency of the measurement object is the frequency on which there is a configured component carrier (PCC and/or SCC), a reference cell is an Scell or Pcell on the frequency of a corresponding measurement object, and the signal quality of a neighboring cell is a designated offset higher than that of the serving cell that has the same frequency point as the neighboring cell; and the event A3 is defined as follows: the frequency of the measurement object refers to all frequencies (including the frequencies at which a PCC and an SCC are operating), the reference cell is a Pcell, and the signal quality of the neighboring cell (if the Scell is on the frequency of the measurement object, then the Scell is treated as the neighboring cell) is a designated offset higher than that of the Pcell. Similar to the co-frequency event A3, a co-frequency event A5 is defined as follows: the frequency of the measurement object is the frequency on which there is the configured component carrier (PCC and/or SCC), the reference cell is an Scell or Pcell on the frequency of the corresponding measurement object, the signal quality of the serving cell is lower than the designated threshold 1, and the signal quality of the neighboring cell is higher than the designated threshold 2; similar to the event A3, the event A5 is defined as follows: the frequency of the measurement object refers to all frequencies (including the frequencies on which there are a PCC and an SCC), the reference cell is the Pcell, the signal quality of the serving cell is lower than the designated threshold 1, and the signal quality of the neighboring cell (if an Scell is on the frequency of the measurement object, then the Scell is treated as the neighboring cell) is higher than the designated threshold 2.
As there may be a plurality of serving cells (only one Pcell, or one Pcell and one or more Scells) in the LTE-A system, the measurement task handover method cannot be used by a single serving cell in an LTE system during the process of a handover or reconstruction.